From the Ekstraliga site .
Great Britain – dates of league matches on Mondays and Thursdays, Sweden – on Tuesdays, Denmark – on Wednesdays, and Poland (PGEE / M2E) – on Fridays, Saturdays and Sundays.
Speedway attendances always strugged at Arlington when not on a Sat evening. From the Ekstraliga website it statea GB dates Mon + Thurs. Not sure that would guarantee the best of attendances at Eastbourne. The crowd generally was not a local one, many travelled a fair distance.